To understand the electron-hole symmetry in \(N_{\mathrm {eff}}\) /Cu between PLCCO and LSCO, we performed further investigations using a complementary experimental technique, ARPES. From comparative photoemission studies between PLCCO and NCCO, we obtained supporting evidence for the smaller spectral weight transfer of PLCCO. Figs. 4(b) and 4(c) show the accumulated energy distribution curves of the PLCCO and NCCO ARPES spectra obtained by integrating the energy dispersion curves along the two high symmetry directions, \(\mathrm {\Gamma }\) -M (nodal) and X-M (anti-nodal), at 10 K. The nominal Ce content of those two compounds is identical (\(x\)  = 0.15). They are optimally oxygenated and have similar \(T_c\) . The ARPES spectra of the QP band for both directions are smaller in PLCCO than in NCCO. On the other hand, the broad spectrum pointed by a red arrow at the energy range of 1.0 – 1.5 eV shows higher intensity in PLCCO, indicating a largely unchanged spectral weight of the ZR band in PLCCO [1]}. These results are consistent with the small \(N_{\mathrm {eff}}\) /Cu of PLCCO observed by the optical measurement. It is worth noting that ARPES measures the filled bands while optical spectroscopy measures the transition from filled to empty bands. Therefore, the energy scale of the optical transition is roughly twice that of ARPES. Our combined spectroscopic studies on PLCCO demonstrate that the \(N_{\mathrm {eff}}\) /Cu of PLCCO is significantly smaller than that of NCCO. Therefore, the \(N_{\mathrm {eff}}\) /Cu is strongly composition-dependent. Because the \(N_{\mathrm {eff}}\) /Cu of electron-doped PLCCO is comparable to that of hole-doped LSCO, our results can be counter-evidence against the long-standing belief of electron-hole asymmetry in \(N_{\mathrm {eff}}\) /Cu.
